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Neutron imaging (NI) is an alternative non-destructive inspection technique compared to the well-known X-ray method. Although neutron imaging data look at a first glance similar to X-ray images it must be underlined that the interaction mechanism of the sample material with neutrons differs fundamentally. X-ray interaction with matter occurs with the electrons in the atomic shells whereas neutrons interact only with the atomic nuclei. Hence, both methods have a different and to great extent complementary contrast origin. Neutron imaging allows for a higher penetration through heavier elements (e.g. metals) whereas a high contrast is given for light elements (e.g. hydrogen). By the use of neutrons instead of X-rays exhaust after-treatment systems can be successfully examined non-destructively for their soot, ash, urea and coating distributions.

Dynamic neutron radiography is a non-destructive inspection method. It provides different attenuation contrast compared, e.g., to common X-ray imaging. This allows neutrons to penetrate centimeter thick layers of metals while fuel or lubricants can still deliver good visibility. With beam cross sections between 3 cm and 30 cm (squared), neutron radiography is an ideal tool for the visualization of running combustion engines. Here we report on an experiment that demonstrates the feasibility to visualize a fired two-stroke chain saw engine running at idle speed (~ 3000 rpm). A sequence of single frames of the running engine was recorded and combined into a movie which provides a view into the moving parts of the engine, the combustion chamber and the crank case.